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Fig. 8 | EvoDevo

Fig. 8

From: Outflow tract septation and the aortic arch system in reptiles: lessons for understanding the mammalian heart

Fig. 8

Outflow tract septation in Crocodylus. Subsequent levels from the proximal (a–e) to the distal OFT. a The septal and parietal cushion are at the same level as the AV cushions (AV). b The OFT is individualized and the parietal and septal cushion form a semicircle. c In the distal OFT the sc presents with NCC condensed mesenchyme (*) adjacent to the first vacuoles of the foramen of Panizza (arrows). Here the sc is apposed to the intercalated cushion. d At this level fusion (#) has occurred between the sc, flanking the folding septum (FS) and the ic separating the systemic from the visceral aorta. e Separation of Pu and Ao is completed, here the ventral myocardial protrusion (Myo) meets the NCC-derived condensed mesenchyme and the two aortae are separated by the flow divider (#). Bar = 100 µm. f Slightly older embryo shows the elaborate vacuolar spaces (arrows) proximal to the SHF separation (#) of both aortae, there is not yet a connection with the sinus of Valsalva (sV). g Cartoon depicts the division of the 4 distal OFT cushions over the 3 main arterial trunks. Note that only the sAO has two cushion derivatives, while the vAo and the Pu have two large cushions plus one small cushion derivative each. The condensed mesenchyme (*) and aortic flow divider (#) are indicated. For clarity all endocardial cushions are shown in one level. Abbreviations as in Fig. 3

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